A Japanese Patent Application Publication (tokkai) No. Heisei 11-227491 published on Aug. 24, 1999 exemplifies a previously proposed vehicular driving operation monitor apparatus which detects an unstable state of a driving operation of a vehicle driver and performs an alarming for the vehicle driver upon a detection of the unstable state. As a technique to calculate an unstability of the driving operation from a smoothness of a steering operation, the previously proposed vehicular driving operation monitor apparatus makes use of a steering entropy method. In the steering entropy method, attention is paid to such a characteristic that a time duration during which the steering operation is not carried out by the vehicle driver, under a load state under which the vehicle driver does not concentrate on the driving of the vehicle due to a load other than the driving, becomes longer than that of an ordinary driving state (an awakened state under no load state), large steering angle errors are accumulated, and a corrected steering quantity becomes large when the vehicle driver returns to pay attention to the driving. The previously proposed driving operation monitor apparatus disclosed in patent literature 1 detects the unstability of the vehicle driver on a basis of a steering entropy value calculated using the steering entropy method described above. Other previously proposed driving support (vehicular driving operation monitor) apparatuses are disclosed in Japanese Patent Application Publications (tokkai)) No. Heisei 8-249600 published on Sep. 27, 1996 and No. 2002-154345 published on May 28, 2002.